Conveying apparatus

ABSTRACT

Provided is a conveying apparatus having simple mechanical and electrical configurations. The conveying apparatus includes: a conveying member that has a dielectric layer having insulating properties and made of an elastomer and a pair of electrode layers placed on both front and back sides of the dielectric layer and having conductive properties, and that is divided into a base portion and a conveying portion being more easily elastically deformed than the base portion and having on its surface a conveying path on which an object to be transported is transported; and a power supply unit that applies between the pair of electrode layers a voltage that changes periodically with time. The conveying portion is elastically extended and contracted with the base portion as a starting point according to a change in the voltage, so that the conveying apparatus transports the object on the conveying path.

TECHNICAL FIELD

The present invention relates to conveying apparatuses capable ofconveying, e.g., powder such as flour and salt and grains such astablets.

BACKGROUND ART

Patent Document 1 discloses a fine powder conveying apparatus. The finepowder conveying apparatus includes a multiplicity of electrodes. Themultiplicity of electrodes are arranged next to each other in aconveying direction. An AC voltage is applied to the multiplicity ofelectrodes in the conveying direction. Powder is attracted by theCoulomb force to move between adjoining ones of the electrodes. PatentDocument 2 discloses a powder handling apparatus including amultiplicity of electrodes arranged next to each other in a conveyingdirection as in Patent Document 1.

RELATED ART DOCUMENTS Patent Documents

Patent Document 1: Japanese Patent Application Publication No.2002-68477 (JP 2002-68477 A)

Patent Document 2: Japanese Patent Application Publication No.H07-327378 (JP H07-327378 A)

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

According to the fine powder conveying apparatus of Patent Document 1and the powder handling apparatus of Patent Document 2, the multiplicityof electrodes need be arranged in the conveying direction along theentire length in the conveying direction of the apparatus, and an ACvoltage need be applied to the multiplicity of electrodes so that powdercan be transported. The fine powder conveying apparatus of PatentDocument 1 and the powder handling apparatus of Patent Document 2therefore have complicated mechanical and electrical configurations. Itis an object of the present invention to provide a conveying apparatushaving simple mechanical and electrical configurations.

Means for Solving the Problem

(1) In order to solve the above problem, a conveying apparatus accordingto the present invention is characterized by including: a conveyingmember that has a dielectric layer having insulating properties and madeof an elastomer and a pair of electrode layers placed on both front andback sides of the dielectric layer and having conductive properties, andthat is divided into a base portion and a conveying portion being moreeasily elastically deformed than the base portion and having on itssurface a conveying path on which an object to be transported istransported; and a power supply unit that applies between the pair ofelectrode layers a voltage that changes periodically with time, whereinthe conveying portion is elastically extended and contracted with thebase portion as a starting point according to a change in the voltage,so that the object is transported on the conveying path.

As used herein, the “AC voltage” refers to a voltage that periodicallychanges with time, and the “DC voltage” refers to a voltage whosepolarity is not inverted. The magnitude of the voltage does not have tobe constant. That is, in this specification, the DC voltage may beconceptually included in the AC voltage. The “AC power supply” refers toa power supply capable of supplying an AC voltage whose polarity isinverted. The “DC power supply” refers to a power supply capable ofsupplying a DC voltage. The DC voltage includes a bias voltage havingconstant magnitude.

The conveying apparatus of the present invention includes the dielectriclayer and the pair of electrode layers. When a voltage is appliedbetween the pair of electrode layers, an electrostatic attractive forceis applied between the pair of electrode layers. The electrostaticattractive force is applied in such a direction that the dielectriclayer, namely the conveying portion, is contracted in a stackingdirection (direction in which the dielectric layer and the electrodelayers are stacked). The dielectric layer is elastically deformable.That is, the dielectric layer has an elastic restoring force. Theelastic restoring force is applied in such a direction that thedielectric layer, namely the conveying portion, is extended in thestacking direction. The conveying portion is thus subjected to theelectrostatic attractive force and the elastic restoring force. Theshape of the conveying portion is elastically changed by the balancebetween these forces.

As the voltage increases, the electrostatic attractive force between thepair of electrode layers increases accordingly. The conveying portion istherefore contracted in the stacking direction against the elasticrestoring force of the dielectric layer. The conveying portion isextended in a planar direction (direction in which the surface of theconveying portion extends) according to the amount of contraction of theconveying portion in the stacking direction. As the voltage decreases,the electrostatic attractive force between the pair of electrode layersdecreases accordingly. The conveying portion is therefore extended inthe stacking direction by the elastic restoring force of the dielectriclayer. The conveying portion is contracted in the planar directionaccording to the amount of extension of the conveying portion in thestacking direction.

The conveying portion can thus be repeatedly elastically extended andcontracted according to a change in voltage. The base portion is lesslikely to be elastically deformed than the conveying portion.Accordingly, the conveying portion can be repeatedly elasticallyextended and contracted with the base portion as a starting point. Inother words, the conveying portion can vibrate with the base portion asa starting point. The conveying portion can transport the object on theconveying path.

According to the conveying apparatus of the present invention, amultiplicity of electrodes need not be placed along the conveying pathalong the entire length of the conveying path. An AC voltage need not beapplied to the multiplicity of electrodes so that the object can betransported. The conveying apparatus therefore has simple mechanical andelectrical configurations. Moreover, the conveying apparatus cantransport the object regardless of electrical characteristics(conductive properties, insulating properties, etc.) of the object.

In typical vibrating conveyors, a hard (e.g., steel) trough having aconveying path is vibrated by a multiplicity of coil springs. The troughitself is not elastically deformed. In the conveying apparatus of thepresent invention, the dielectric layer is made of a flexible (lowYoung's modulus) elastomer. The dielectric layer can therefore absorbthe impact of the vibration of the conveying portion on the object.Accordingly, the object is less likely to be damaged by the vibration ofthe conveying portion when the object is being transported.

(1-1) In the configuration of (1), a stacking direction is a directionin which the dielectric layer and the electrode layers are stacked, anda conveying direction is a direction in which the conveying path extendson the surface of the conveying portion. A contracted state is a statewhere the conveying portion has been extended to the maximum in thestacking direction and has been contracted to the maximum in theconveying direction, and an extended state is a state where theconveying portion has been contracted to the maximum in the stackingdirection and has been extended to the maximum in the conveyingdirection. Extension acceleration is acceleration of deformation of theconveying path in the conveying direction when the conveying pathswitches from the contracted state to the extended state, andcontraction acceleration is acceleration of deformation of the conveyingpath in the conveying direction when the conveying path switches fromthe extended state to the contracted state. It is desirable that theextension acceleration be different from the contraction acceleration.

In the case where the acceleration of deformation of the conveying pathis small, the object is less likely to be shifted with respect to theconveying path when the conveying path is deformed. Accordingly, theobject tends to move according to deformation of the conveying path. Onthe other hand, in the case where the acceleration of deformation of theconveying path is large, the object tends to be shifted with respect tothe conveying path when the conveying path is deformed. Accordingly, theobject is less likely to move according to deformation of the conveyingpath.

According to this configuration, the acceleration of deformation variesbetween when the conveying path switches from the contracted state tothe extended state and when the conveying path switches from theextended state to the contracted state. Accordingly, the object can bepreferentially moved either when the conveying path switches from thecontracted state to the extended state or when the conveying pathswitches from the extended state to the contracted state. According tothis configuration, the conveying direction of the object can thereforebe controlled.

(2) In the configuration of (1), it is preferable that a conveyingdirection be a direction in which the conveying path extends on thesurface of the conveying portion, and the base portion be placed at oneend or the other end of the conveying path in the conveying direction.

According to this configuration, the conveying portion can be vibratedalong the entire length of the converting path with the base portion asa starting point. This can increase the distance by which the object istransported in one stroke (from the contracted state through theextended state to the contracted state or from the extended statethrough the contracted state to the extended state).

(3) In the configuration of (1) or (2), it is preferable that theconveying apparatus further include a restraining member that restrainsa part of the conveying member, and the base portion be formed byrestraining the part of the conveying member by the restraining member.

According to this configuration, a part of the conveying member isrestrained by the restraining member, whereby the conveying member canbe divided into the base portion and the conveying portion. That is, apart of the conveying member is restrained by the restraining member,whereby the base portion can be set in the part of the conveying member,and the conveying portion can be set in the remaining part of theconveying member (the part that is not restrained by the restrainingmember). According to this configuration, elastic deformation andpositional shifting of the base portion associated with vibration of theconveying portion can be suppressed.

(4) In the configuration of any one of (1) to (3), it is preferable thatthe conveying direction be the direction in which the conveying pathextends on the surface of the conveying portion, a lateral direction bea direction perpendicular to the conveying direction, and a total lengthof the conveying path in the conveying direction be larger than that ofthe conveying path in the lateral direction.

According to this configuration, the amount of extension/contraction ofthe conveying path can be made larger in the conveying direction than inthe lateral direction. This can increase the distance by which theobject is transported in one stroke.

(5) In the configuration of any one of (1) to (4), it is preferable thatthe conveying member have a protective layer having insulatingproperties and made of an elastomer, the protective layer being placedon the frontmost electrode layer.

The protective layer is made of an elastomer and is flexible. Accordingto this configuration, the electrode layer can therefore be protectedfrom the outside. The protective layer has insulating properties.According to this configuration, the electrode layer can thus beelectrically insulated from the outside.

(6) In the configuration of any one of (1) to (5), it is preferable thatthe conveying apparatus further include: a backing member that is placedon a back side of the conveying member and that slide-contacts theconveying portion when the conveying portion is elastically extended andcontracted. According to this configuration, the conveying member canslide-contact the backing member when being elastically deformed.

(6-1) In the configuration of (6), it is preferable that the backingmember be made of a resin or a metal. This configuration reducesfrictional resistance that is caused when the conveying portionslide-contacts the backing member. Elastic defonnation of the conveyingportion is therefore less likely to be restricted by the backing member.

(7) In the configuration of any one of (1) to (6), it is preferable thatthe power supply unit have a DC power supply capable of supplying avoltage whose polarity is not inverted (i.e., a DC voltage) or an ACpower supply capable of supplying a voltage whose polarity is invertedand a waveform adjustment unit that adjusts a waveform of the voltagethat is supplied from the DC power supply or the AC power supply.According to this configuration, the waveform of the voltage that issupplied from the DC power supply or the AC power supply can be adjustedby the waveform adjustment unit.

(8) In the configuration of any one of (1) to (6), it is preferable thatthe power supply unit have a DC power supply capable of supplying a biasvoltage whose polarity is not inverted and which has constant magnitudeand an AC power supply capable of supplying a voltage whose polarity isinverted. According to this configuration, the DC voltage and the ACvoltage can be applied to the conveying member so as to be superimposedon each other. The AC voltage can therefore be applied to the conveyingmember based on a predetermined bias voltage.

(9) In the configuration of any one of (1) to (8), it is preferable thatthe voltage that is applied between the pair of electrode layers by thepower supply unit be a DC voltage whose polarity is not inverted.According to this configuration, a voltage which changes periodicallywith time and whose polarity is not inverted can be applied between thepair of electrode layers.

(9-1) In the configuration of (9), it is preferable that the DC voltagehave one of a triangular waveform, a sawtooth waveform, and arectangular waveform. According to this configuration, the waveform canbe easily produced. Extension and contraction of the conveying portioncan therefore be easily controlled.

(9-2) In the configuration of (9), it is preferable that a waveform of achange in the DC voltage with time is a continuous waveform or a pulsewaveform. According to this configuration, the frequency can be easilyadjusted. The conveying speed can therefore be easily controlled.

(10) In the configuration of (9), it is preferable that a waveform, forone period, of a change in the DC voltage with time have a boost sectionwhere the DC voltage increases with time and a step-down section wherethe DC voltage decreases with time, and an absolute value of a timedifferential value of the DC voltage in the boost section be smallerthan that of the time differential value of the DC voltage in thestep-down section.

As used herein, the “time differential value of the DC voltage” refersto the time rate of change of the DC voltage (dV/dt, gradient), where Vrepresents the DC voltage and t represents time. In the case where thetime differential value of the DC voltage is not constant in the boostsection and the step-down section, that is, in the case where asecond-order time differential value (d²V/dt²) is not 0, the “absolutevalue of the time differential value” refers to the maximum value of theabsolute value of the time differential value. For example, in the casewhere there is a plurality of sections (a linear section, a curvedsection having a constant curvature, a curved section in which thecurvature varies, etc.) in the boost section or the step-down section,the “absolute value of the time differential value” refers to thelargest one of the absolute values of the time differential values inthe plurality of sections.

The conveying portion is extended so as to correspond to the boostsection. That is, the conveying portion switches from the contractedstate to the extended state of (1-1). The time differential value of theDC voltage in the boost section corresponds to the extensionacceleration in (1-1). The larger the absolute value of the timedifferential value is, the larger the extension acceleration is.

The conveying portion is contracted so as to correspond to the step-downsection. That is, the conveying portion switches from the extended stateto the contracted state of (1-1). The time differential value of the DCvoltage in the step-down section corresponds to the contractionacceleration in (1-1). The larger the absolute value of the timedifferential value is, the larger the contraction acceleration is.

According to this configuration, the absolute value of the timedifferential value of the DC voltage in the boost section is smallerthan that of the time differential value of the DC voltage in thestep-down section. The conveying portion can therefore be slowlyextended and quickly contracted. Accordingly, the object is less likelyto be shifted with respect to the transport path when the conveyingportion is extended. The object therefore tends to move according toextension of the conveying portion. Moreover, the object tends to beshifted with respect to the transport path when the conveying portion iscontracted. The object is therefore less likely to move according tocontraction of the conveying portion

As described above, this configuration uses inertia of the object,whereby the object can be efficiently transported when the conveyingportion is extended. Moreover, movement of the object in the reversedirection can be suppressed when the conveying portion is contracted.

(11) In the configuration of any one of (1) to (10), it is preferablethat the conveying apparatus further include: a control unit thatcontrols the power supply unit. According to this configuration, thewaveform, period, etc. of the voltage can be controlled by the controlunit via the power supply unit.

(11-1) In the configuration of (11), it is preferable that the controlunit control the power supply so that the voltage has a predeterminedwaveform and a predetermined period. According to this configuration,the waveform and the period of the voltage can be set to predeterminedvalues. The waveform and the period of the voltage may be stored in amemory unit of the control unit.

(12) In the configuration of (11), it is preferable that the conveyingapparatus further include: a detection unit that detects extension andcontraction of the conveying portion, and the control unit control thepower supply unit based on a detection value of the detection unit.According to this configuration, the power supply unit can be controlledbased on extension and contraction of the conveying portion. Forexample, when the conveying portion switches from the extended statethrough the contracted state to the extended state of (1-1), the controlunit may start extending the conveying portion by using the power supplyunit after verifying that contraction of the conveying portion has beencompleted by using the detection unit. This can ensure a similarconveying speed and reduce the frequency of the voltage that is appliedfrom the power supply unit to the pair of electrode layers, as comparedto the case where the control unit starts extending the conveyingportion before contraction of the conveying portion is completed.

(12-1) In the configuration of (12), it is preferable that a detectionposition be set on the conveying path, and the detection unit be adisplacement sensor that detects displacement of the detection positionwhich is associated with extension and contraction of the conveyingportion. According to this configuration, the power supply unit can becontrolled based on the displacement of the detection position.

(13) In the configuration of any one of (1) to (12), it is preferablethat the conveying direction be the direction in which the conveyingpath extends on the surface of the conveying portion, the lateraldirection be the direction perpendicular to the conveying direction, theelectrode layer have a plurality of strip portions extending in theconveying direction and arranged next to each other in the lateraldirection, and clearance be provided between a pair of the stripportions adjacent to each other in the lateral direction.

According to this configuration, the clearance is provided between thepair of strip portions adjacent to each other in the lateral direction.This can reduce the area of the electrode layers as compared to the casewhere the clearance is not provided, and can therefore reduce a currentvalue required to drive the conveying portion while ensuring a similaror higher conveying speed as compared to the case where the clearance isnot provided. According to this configuration, the pair of stripportions adjacent to each other in the lateral direction is less likelyto restrict extension and contraction of each other's strip portion. Theplurality of strip portions are therefore easily extended and contractedin the conveying direction.

Effects of the Invention

The present invention can provide a conveying apparatus having simplemechanical and electrical configurations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a conveying apparatus of a first embodiment.

FIG. 2 is a sectional view taken in the direction II-II in FIG. 1.

FIG. 3 is a schematic diagram of a voltage that is applied to aconveying member.

FIG. 4A is a sectional view taken in the left-right direction, showing acontracted state (first contracted state) of the conveying apparatus.FIG. 4B is a sectional view taken in the left-right direction, showingan extended state (first extended state) of the conveying apparatus.FIG. 4C is a sectional view taken in the left-right direction, showing acontracted state (second contracted state) of the conveying apparatus.FIG. 4D is a sectional view taken in the left-right direction, showingan extended state (second extended state) of the conveying apparatus.

FIG. 5 is a sectional view of a conveying apparatus of a secondembodiment taken in the front-rear direction.

FIG. 6 is a sectional view of a conveying apparatus of a thirdembodiment taken in the front-rear direction.

FIG. 7 is a sectional view of a conveying apparatus of a fourthembodiment taken in the left-right direction.

FIG. 8 is a top view of a conveying apparatus of a fifth embodiment.

FIG. 9 is a top view of a conveying apparatus of a further embodiment(first further embodiment).

FIG. 10 is a sectional view of a conveying apparatus of a furtherembodiment (second further embodiment) taken in the left-rightdirection.

FIG. 11 is a graph showing a change in position with time in the casewhere a voltage has a rectangular waveform.

FIG. 12 is a graph showing a change in distance with time in the case ofFIG. 11.

FIG. 13 is a graph showing a change in position with time in the casewhere a voltage has a right triangular waveform with a sharplyincreasing gradient to the right.

FIG. 14 is a graph showing a change in distance with time in the case ofFIG. 13.

FIG. 15 is a graph showing a change in position with time in the casewhere a voltage has a right triangular waveform with a sharplyincreasing gradient to the left.

FIG. 16 is a graph showing a change in position with time in the casewhere a voltage has an isosceles triangular waveform.

FIG. 17 is a graph showing a change in position with time in the casewhere a voltage has a triangular waveform with a sharply increasinggradient to the right.

FIG. 18 is a graph showing a change in position with time in the casewhere a voltage has a right triangular waveform with a sharplyincreasing gradient to the right.

FIG. 19 is a graph showing a change in distance with time in the case ofFIGS. 15 to 19.

FIG. 20 is a graph showing a change in position with time in the casewhere a voltage has a right triangular waveform with a sharplyincreasing gradient to the right and an interval during which thevoltage is off is set between each pair of waves that are located nextto each other in chronological order.

FIG. 21 is a graph showing a change in distance with time in the case ofFIG. 20.

FIG. 22 is a graph showing a change in position with time in the casewhere a voltage has a right triangular waveform with a sharplyincreasing gradient to the right.

FIG. 23 is a graph showing acceleration of extension/contraction of aconveying portion in the case of FIG. 22.

FIG. 24 is a graph showing a change in distance with time in the case ofFIG. 22.

MODES FOR CARRYING OUT THE INVENTION

Embodiments of a conveying apparatus of the present invention will bedescribed below. In the drawings described below, the upper sidecorresponds to the “front side” of the present invention, the lower sidecorresponds to the “back side” of the present invention, the left-rightdirection corresponds to the “conveying direction” of the presentinvention, and the front-rear direction corresponds to the “lateraldirection” of the present invention. The up-down direction correspondsto the “stacking direction,” and the front-rear and left-rightdirections correspond to the “planar direction.”

First Embodiment Configuration of Conveying Apparatus

First, the configuration of a conveying apparatus of the presentembodiment will be described. FIG. 1 is a top view of the conveyingapparatus of the present embodiment. FIG. 2 is a sectional view taken inthe direction II-II in FIG. 1. For convenience of description, thethickness in the up-down direction of the conveying apparatus is shownexaggerated in FIG. 2. As shown in FIGS. 1 and 2, the conveyingapparatus 1 of the present embodiment includes a conveying member 2, arestraining member 30, a backing member 31, a pair of front and rearconnectors 32, and a power supply unit 4.

The conveying member 2 includes a total of five dielectric layers 20, atotal of six electrode layers 21, and a pair of upper and lowerprotective layers 23. The dielectric layers 20 are made of hydrogenatednitrile rubber (H-NBR) and have a rectangular shape that is long in theleft-right direction. H-NBR is included in the concept of the“elastomer” of the present invention. The dielectric layers 20 areflexible and have insulating properties. Each dielectric layer 20 has athickness of 20 μm in the stacking direction.

The electrode layers 21 are made of an electrode material as acrylicrubber filled with carbon powder. The electrode layers 21 are formed byprinting paint containing the electrode material onto the dielectriclayers 20. The electrode layers 21 have a rectangular shape that is longin the left-right direction. The electrode layers 21 are flexible andhave conductive properties. Each electrode layer 21 has a thickness of15 μm in the stacking direction.

The six electrode layers 21 and the five dielectric layers 20 arealternately stacked in the up-down direction. The dielectric layer 20 isinterposed between each pair of electrode layers 21 adjacent to eachother in the up-down direction. The odd numbered (first, third, andfifth) electrode layers 21 from the top are electrically connected to anAC power supply 40 described below. The even numbered (second, fourth,and sixth) electrode layers 21 from the top are electrically connectedto a DC power supply 41 described below.

The protective layers 23 are made of butyl rubber (IIR) and have arectangular shape that is long in the left-right direction. IIR isincluded in the concept of the “elastomer” of the present invention. Theprotective layers 23 are flexible and have insulating properties. Eachprotective layer 23 has a thickness of 5 μm in the stacking direction.The upper protective layer 23 is placed on the upper side of theuppermost electrode layer 21. The lower protective layer 23 is stackedon the lower side of the lowermost electrode layer 21.

The conveying member 2 is divided into a base portion 2 a and aconveying portion 2 b. The base portion 2 a is restrained in the up-downdirection by the restraining member 30 described below. The base portion2 a is set at the left end of a conveying path 22 described below bythis restraint. The conveying portion 2 b is set on the right side ofthe base portion 2 a. The conveying portion 2 b can alternately switchbetween an extended state and a contracted state according to a changein voltage described below. That is, the conveying portion 2 b canvibrate. The conveying path 22 is disposed on the upper surface of theconveying portion 2 b (specifically, the upper surface of the upperprotective layer 23). The conveying path 22 extends linearly in theleft-right direction. The left end of the conveying path 22 correspondsto the upstream end in the conveying direction, and the right end of theconveying path 22 corresponds to the downstream end in the conveyingdirection.

The restraining member 30 is made of a hard resin and has the shape of aclamp. The restraining member 30 has insulating properties. Therestraining member 30 sandwiches the base portion 2 a in the up-downdirection. Elastic deformation of the base portion 2 a is thusrestricted as compared to the conveying portion 2 b.

The backing member 31 is made of a hard acrylic resin and has arectangular shape that is long in the left-right direction. The backingmember 31 has insulating properties. The backing member 31 is disposedon the lower side of the conveying member (specifically, on the lowerside of the lower protective layer 23). The backing member 31 has a flat(smooth) upper surface. The restraining member 30 is fixed to the leftedge of the upper surface of the backing member 31. That is, the baseportion 2 a is fixed to the backing member 31 via the restraining member30. The conveying portion 2 b is not fixed to the backing member 31.When the conveying portion 2 b switches between the extended state andthe contracted state as described below, the lower surface of theconveying portion 2 b (specifically, the lower surface of the lowerprotective layer 23) slide-contacts the upper surface of the backingmember 31.

The connectors 32 connect to the base portion 2 a. The front connector32 is electrically connected to the odd numbered electrode layers 21from the top via a wire (not shown) that is made of silver paste andplaced in the base portion 2 a. The rear connector 32 is electricallyconnected to the even numbered electrode layers 21 from the top via awire (not shown) placed in the base portion 2 a.

The power supply unit 4 includes the AC power supply 40 and the DC powersupply 41. The AC power supply 40 is electrically connected to the frontconnector 32. The DC power supply 41 is electrically connected to therear connector 32.

FIG. 3 is a schematic diagram of a voltage that is applied to theconveying member. As shown in FIG. 3, the AC power supply 40 applies anAC voltage of a sinusoidal waveform to the conveying member 2. The DCpower supply 41 applies a DC voltage (bias voltage) to the conveyingmember 2. Specifically, the AC power supply 40 produces a voltage whosepolarity is inverted at 0 V. The DC power supply 41 produces a biasvoltage of constant magnitude. The DC voltage and the AC voltage areapplied to the conveying member 2 so as to be superimposed on eachother. The amplitude Vp of the AC voltage is smaller than the DC voltageVdc. A peak-to-peak value Vpp is the difference between maximum andminimum values Vmax, Vmin of the AC voltage. The peak-to-peak value Vppis twice the amplitude Vp.

Movement of Conveying Apparatus

Movement of the conveying apparatus of the present embodiment will bedescribed below. FIG. 4A is a sectional view taken in the left-rightdirection, showing a contracted state (first contracted state) of theconveying apparatus of the present embodiment. FIG. 4B is a sectionalview taken in the left-right direction, showing an extended state (firstextended state) of the conveying apparatus of the present embodiment.FIG. 4C is a sectional view taken in the left-right direction, showing acontracted state (second contracted state) of the conveying apparatus ofthe present embodiment. FIG. 4D is a sectional view taken in theleft-right direction, showing an extended state (second extended state)of the conveying apparatus of the present embodiment. For convenience ofdescription, the thickness in the up-down direction of the conveyingapparatus is shown exaggerated in FIGS. 4A to 4D. FIG. 4A corresponds topoint A in FIG. 3, FIG. 4B corresponds to point B in FIG. 3, FIG. 4Ccorresponds to point C in FIG. 3, and FIG. 4D corresponds to point D inFIG. 3.

As described above, the base portion 2 a of the conveying member 2 isfixed to the backing member 31 via the restraining member 30.Accordingly, if a voltage is applied to the conveying member 2, theconveying portion 2 b repeatedly switches between the contracted stateshown in FIGS. 4A and 4C and the extended state shown in FIGS. 4B and 4Dwith the base portion 2 a as a starting point. That is, the conveyingportion 2 b vibrates according to the frequency of the voltage shown inFIG. 3.

(Movement of Conveying Apparatus when Switching from Contracted State toExtended State)

First, movement of the conveying portion 2 b when the conveying portion2 b switches from the contracted state shown in FIGS. 4A and 4C to theextended state shown in FIGS. 4B and 4D will be described. In thecontracted state shown in FIGS. 4A and 4C, a voltage of the minimumvalue Vmin is applied to the conveying portion 2 b as shown by points A,C in FIG. 3. A minimum electrostatic attractive force is thereforeapplied between each pair of electrode layers 21 adjacent to each otherin the up-down direction. Accordingly, the conveying portion 2 b isextended to the maximum in the up-down direction and contracted to themaximum in the horizontal direction by an elastic restoring force of thefive dielectric layers 20 and the six electrode layers 21.

As the voltage applied to the conveying portion 2 b increases as shownfrom point A to point B or from point C to point D in FIG. 3, theelectrostatic attractive force between each pair of electrode layers 21adjacent to each other in the up-down direction increases accordingly.The conveying portion 2 b is therefore contracted in the up-downdirection and extended in the horizontal direction against the overallelastic restoring force of the five dielectric layers 20 and the sixelectrode layers 21, as shown from FIG. 4A to FIG. 4B and from FIG. 4Cto FIG. 4D. As shown in FIG. 1, the total length of the conveying path22 in the left-right direction is longer than that of the conveying path22 in the front-rear direction. The amount of extension of the conveyingpath 22 is therefore larger in the left-right direction than in thefront-rear direction.

In the extended state shown in FIGS. 4B and 4D, a voltage of the maximumvalue Vmax is applied to the conveying portion 2 b as shown by points B,D in FIG. 3. A maximum electrostatic attractive force is thereforeapplied between each pair of electrode layers 21 adjacent to each otherin the up-down direction. Accordingly, the conveying portion 2 b iscontracted to the maximum in the up-down direction and extended to themaximum in the horizontal direction. In the extended state, the overallelastic restoring force of the five dielectric layers 20 and the sixelectrode layers 21 is accumulated in the conveying portion 2 b. Theconveying portion 2 b switches from the contracted state to the extendedstate in this manner.

(Movement of Conveying Apparatus when Switching from Extended State toContracted State)

Next, movement of the conveying portion 2 b when the conveying portion 2b switches from the extended state shown in FIG. 4B to the extendedstate shown in FIG. 4C will be described. As the voltage applied to theconveying portion 2 b decreases as shown from point B to point C in FIG.3, the electrostatic attractive force between each pair of electrodelayers 21 adjacent to each other in the up-down direction decreasesaccordingly. The conveying portion 2 b is therefore extended in theup-down direction and contracted in the horizontal direction by theoverall elastic restoring force of the five dielectric layers 20 and thesix electrode layers 21 as shown from FIG. 4B to FIG. 4C. As shown inFIG. 1, the total length of the conveying path 22 in the left-rightdirection is longer than that of the conveying path 22 in the front-reardirection. The amount of contraction of the conveying path 22 istherefore larger in the left-right direction than in the front-reardirection. The conveying portion 2 b switches from the extended state tothe contracted state in this manner.

(Relationship Between Extension Acceleration and ContractionAcceleration)

The relationship between extension acceleration and contractionacceleration will be described below. Extension acceleration a1 refersto acceleration of deformation of the conveying path 22 in theleft-right direction when the conveying path 22 switches from thecontracted state shown in FIGS. 4A and 4C to the extended state shown inFIGS. 4B and 4D. Contraction acceleration a2 refers to acceleration ofdeformation of the conveying path 22 in the left-right direction whenthe conveying path 22 switches from the extended state shown in FIG. 4Bto the contracted state shown in FIG. 4C. The relationship of extensionacceleration a1<contraction acceleration a2 is satisfied in the presentembodiment. The conveying path 22 therefore slowly switches from thecontracted state to the extended state and quickly switches from theextended state to the contracted state.

For example, the acceleration of deformation of the conveying path 22can be calculated from acceleration of movement in the left-rightdirection of any point on the conveying path 22 at the time theconveying path 22 switches from the contracted state to the extendedstate or from the extended state to the contracted state.

(Movement of Object to be Transported)

Movement of an object W to be transported by the conveying apparatus ofthe present embodiment will be described. As shown in FIGS. 4A to 4D,the object W to be transported moves from left to right on the conveyingpath 22 according to the change in voltage shown in FIG. 3.

When switching from the contracted state to the extended state as shownfrom FIG. 4A to FIG. 4B, the conveying path 22 is extended to the rightwith the base portion 2 a as a starting point. The extensionacceleration a1 of the conveying path 22 is low at the time theconveying path 22 switches from the contracted state to the extendedstate. The object W is therefore less likely to be shifted in theleft-right direction with respect to the conveying path 22. Accordingly,the object W moves to the right from position P1 to position P2 as theconveying path 22 is extended.

When switching from the extended state to the contracted state as shownfrom FIG. 4B to FIG. 4C, the conveying path 22 is contracted to the leftwith the base portion 2 a as a starting point. The contractionacceleration a2 of the conveying path 22 is high at the time theconveying path 22 switches from the extended state to the contractedstate. The object W therefore tends to be shifted in the left-rightdirection with respect to the conveying path 22. In addition, whenswitching from the extended state to the contracted state, the conveyingportion 2 b is extended in the up-down direction by the elasticrestoring force. The object W therefore tends to bounce upward from theconveying path 22. In this regard as well, the object W tends to beshifted in the left-right direction with respect to the conveying path22. The object W therefore does not move back from position P2 toposition P1 even through the conveying path 22 is contracted. The objectW stays at position P2.

When the conveying path 22 switches again from the contracted state tothe extended state as shown from FIG. 4C to FIG. 4D, the object W movesto the right from position P2 to position P3 as the conveying path 22 isextended, as in the case from FIG. 4A to FIG. 4B.

As described above, the object W moves little by little from left toright on the conveying path 22 as the conveying portion 2 b repeatedlyswitches between the contracted state and the extended state. That is,the object W is moved by a predetermined pitch (=P2−P1=P3−P2) when theconveying portion 2 b switches from the contracted state to the extendedstate. The object W stops when the conveying portion 2 b switches fromthe extended state to the contracted state.

Functions and Effects

Functions and effects of the conveying apparatus of the presentembodiment will be described below. According to the conveying apparatus1 of the present embodiment, the conveying portion 2 b can repeatedlyswitch between the extended state shown in FIGS. 4B and 4D and thecontracted state shown in FIGS. 4A and 4C with the base portion 2 a as astarting point. In other words, the conveying portion 2 b can vibratewith the base portion 2 a as a starting point. The conveying portion 2 bcan transport the object W on the conveying path 22 by this vibration.

According to the conveying apparatus 1 of the present embodiment, amultiplicity of electrodes need not be placed along the conveying path22 along the entire length of the conveying path 22. An AC voltage neednot be applied to the multiplicity of electrodes so that the object Wcan be transported. The conveying apparatus 1 of the present embodimenttherefore has simple mechanical and electrical configurations. Moreover,the conveying apparatus 1 of the present embodiment can transport theobject W regardless of electrical characteristics (conductiveproperties, insulating properties, etc.) of the object W.

In typical vibrating conveyors, a hard (e.g., steel) trough having theconveying path 22 is vibrated by a multiplicity of coil springs. Thetrough itself is not elastically deformed. In the conveying apparatus 1of the present embodiment, the dielectric layers 20 are made of aflexible (low Young's modulus) elastomer. The dielectric layers 20 cantherefore absorb the impact of the vibration of the conveying portion 2b on the object W. Accordingly, the object W is less likely to bedamaged by the vibration of the conveying portion 2 b when the object Wis being transported.

According to the conveying apparatus 1 of the present embodiment, therelationship of extension acceleration a1<contraction acceleration a2 issatisfied regarding acceleration of deformation in the left-rightdirection of the conveying path 22. The conveying portion 2 b thereforeslowly switches from the contracted state to the extended state andquickly switches from the extended state to the contracted state. Theconveying direction of the object W can thus be controlled to thedirection from left to right.

According to the conveying apparatus 1 of the present embodiment, asshown in FIGS. 4A to 4D, the base portion 2 a connects to the left endof the conveying portion 2 b. The conveying portion 2 b can therefore bevibrated along the entire length in the left-right direction of theconveying path 22 with the base portion 2 a as a starting point. Thiscan increase the distance by which the object W is transported in onestroke (from the contracted state through the extended state to thecontracted state).

According to the conveying apparatus 1 of the present embodiment, asshown in FIG. 3, the DC voltage and the AC voltage can be applied to theconveying member 2 so as to be superimposed on each other. Accordingly,the AC voltage (the voltage that changes periodically with time) can beapplied to the conveying member 2 based on a predetermined bias voltage.

According to the conveying apparatus 1 of the present embodiment, asshown in FIGS. 1 and 2, a part of the conveying member 2 is restrainedby the restraining member 30, whereby the conveying member 2 can bedivided into the base portion 2 a and the conveying portion 2 b. Thatis, a part of the conveying member 2 is restrained by the restrainingmember 30, whereby the base portion 2 a can be set in the part of theconveying member 2, and the conveying portion 2 b can be set in theremaining part of the conveying member 2 (the part that is notrestrained by the restraining member 30). As shown in FIGS. 4A to 4D,elastic deformation and positional shifting of the base portion 2 a canbe suppressed even when the conveying portion 2 b vibrates.

The base portion 2 a includes the left edges of the electrode layers 21.The connectors 32 are disposed on the left side of the base portion 2 a(the opposite side of the base portion 2 b from the conveying portion 2b). As shown in FIGS. 4A to 4D, the electrode layers 21 are less likelyto be electrically disconnected from the connectors 32 even when theconveying portion 2 b vibrates.

As shown in FIG. 1, the total length in the left-right direction of theconveying path 22 of the conveying apparatus 1 of the present embodimentis larger than that in the front-rear direction of the conveying path22. The amount of extension/contraction of the conveying path 22 istherefore larger in the left-right direction than in the front-reardirection. This can increase the distance by which the object W istransported in one stroke (from the contracted state through theextended state to the contracted state) as compared to the case wherethe conveying direction is the front-rear direction.

As shown in FIG. 2, the conveying apparatus 1 of the present embodimentincludes the pair of upper and lower protective layers 23. Theprotective layers 23 are made of IIR and are flexible. According to theconveying apparatus 1 of the present embodiment, the uppermost andlowermost electrode layers 21 can therefore be protected from theoutside. The protective layers 23 have insulating properties. Accordingto the conveying apparatus 1 of the present embodiment, the uppermostand lowermost electrode layers 21 can thus be electrically insulatedfrom the outside.

As shown in FIGS. 4A to 4D, the conveying apparatus 1 of the presentembodiment includes the backing member 31. The conveying portion 2 b cantherefore slide-contact the backing member 31 when elastically deformed.The backing member 31 is made of a hard acrylic resin. This can reducefrictional resistance that is caused when the conveying portion 2 bslide-contacts the backing member 31, as compared to the case where thebacking member 31 is made of an elastomer. Elastic deformation of theconveying portion 2 b is less likely to be restricted by the backingmember 31.

Second Embodiment

A conveying apparatus of the present embodiment is different from thatof the first embodiment in that two conveying apparatuses are arrangednext to each other in the front-rear direction. Only the difference willbe described below. FIG. 5 is a sectional view of the conveyingapparatus of the present embodiment taken in the front-rear direction.Those portions corresponding to FIG. 2 are denoted by the same referencecharacters.

As shown in FIG. 5, a conveying unit 10 includes two conveyingapparatuses 1. The two conveying apparatuses 1 are arranged next to eachother in the front-rear direction (lateral direction) so as to beshifted from each other in the up-down direction. There is a differencein level between two conveying paths 22. An overlapping portion O1 islocated between the two conveying apparatuses 1. In the overlappingportion O1, the rear edge of the front conveying apparatus 1 overlapsthe front edge of the rear conveying apparatus 1 as viewed from above.Clearance L1 in the up-down direction in the overlapping portion O1 issmaller than the diameter of an object W to be transported. The object Wis therefore less likely to drop from the overlapping portion O1.

The conveying apparatus of the present embodiment and the conveyingapparatus of the first embodiment have similar functions and effectsregarding those portions having the same configuration. The twoconveying apparatuses 1 are arranged next to each other in thefront-rear direction. This can increase the amount by which the object Wis transported per unit time.

Third Embodiment

A conveying apparatus of the present embodiment is different from thatof the second embodiment in that a cushioning member is interposedbetween two conveying apparatuses. Only the difference will be describedbelow. FIG. 6 is a sectional view of the conveying apparatus of thepresent embodiment taken in the front-rear direction. Those portionscorresponding to FIG. 5 are denoted by the same reference characters.

As shown in FIG. 6, two conveying apparatuses 1 are arranged next toeach other in the front-rear direction (lateral direction). There is nodifference in level between two conveying paths 22. A cushioning member91 made of a foamed elastomer is interposed between the two conveyingapparatuses 1. The cushioning member 91 is in the form of sponge. Thecushioning member 91 is flexible and has insulating properties. Thespring constant in the front-rear direction of the cushioning member 91is smaller than that in the front-rear direction of the conveyingapparatus 1.

The conveying apparatus of the present embodiment and the conveyingapparatus of the second embodiment have similar functions and effectsregarding those portions having the same configuration. According to theconveying apparatus 1 of the present embodiment, the flexible cushioningmember 91 is interposed between the two conveying apparatuses 1.Accordingly, the cushioning member 91 can absorb elastic deformation inthe front-rear direction when the conveying apparatus 1 switches fromthe contracted state (see FIGS. 4A and 4C) to the extended state (seeFIGS. 4B and 4D). Elastic deformation of one of the conveyingapparatuses 1 is therefore less likely to hinder elastic deformation ofthe other conveying apparatus 1 between the two conveying apparatuses 1.The two conveying apparatuses 1 can therefore be driven independently.

Fourth Embodiment

A conveying apparatus of the present embodiment is different from thatof the first embodiment in that a control unit and a displacement sensorare provided. Only the difference will be described below. FIG. 7 is asectional view of the conveying apparatus of the present embodimenttaken along the front-rear direction. Those portions corresponding toFIG. 2 are denoted by the same reference characters.

As shown in FIG. 7, a conveying apparatus 1 includes a control unit 5and a displacement sensor 6. A power supply unit 4 includes an AC powersupply 40 and a waveform adjustment unit 42. The displacement sensor 6is included in the concept of the “detection unit” of the presentinvention. The displacement sensor 6, the control unit 5, and thewaveform adjustment unit 42 are electrically connected to each other. Adetection position P4 is set on a conveying path 22. The displacementsensor 6 detects displacement of the detection position P4 which isassociated with extension and contraction of a conveying portion 2 b.The control unit 5 controls the waveform adjustment unit 42 based on thedetection value of the displacement sensor 6, namely displacement of thedetection position P4. The waveform adjustment unit 42 adjusts thefrequency, waveform, maximum value Vmax, minimum value Vmin, etc. of anAC voltage that is supplied from the AC power supply 40.

The conveying apparatus of the present embodiment and the conveyingapparatus of the first embodiment have similar functions and effectsregarding those portions having the same configuration. According to theconveying apparatus 1 of the present embodiment, the voltage can beadjusted by the waveform adjustment unit 42 according to the conveyingspeed and the properties (volume, mass, shape, etc.) of an object W tobe transported.

For example, in the case where the AC voltage has a sinusoidal waveform,the waveform adjustment unit 42 can generate pulse waves (solitarywaves) from the AC voltage. The waveform adjustment unit 42 can alsoadjust the pulse width or the period of the pulse waves based on thedetection value of the displacement sensor 6, namely displacement of thedetection position P4. That is, the waveform adjustment unit 42 canadjust the interval between each pair of pulse waves that are locatednext to each other in chronological order. Specifically, the controlunit 5 can use the displacement sensor 6 to check if contraction of theconveying portion 2 b has been completed at the time the conveyingportion 2 b switches from the extended state shown in FIG. 4B to thecontracted state shown in FIG. 4C (a voltage of 0 V in the case wherethe voltage shown in FIG. 3 has a pulse waveform). After verifying thatcontraction of the conveying portion 2 b has been completed, the controlunit 5 can use the waveform adjustment unit 42 to start extending theconveying portion 2 b (switching the conveying portion 2 b from thecontracted state shown in FIG. 4C to the extended state shown in FIG.4D). This can reduce the frequency of the voltage shown in FIG. 3 whilemaintaining a similar conveying speed, as compared to the case where theconveying portion 2 b starts being extended before contraction of theconveying portion 2 b is completed.

Fifth Embodiment

A conveying apparatus of the present embodiment is different from thatof the first embodiment in that each electrode layer includes aplurality of strip portions. Only the difference will be describedbelow. FIG. 8 is a top view of the conveying apparatus of the presentembodiment. Those portions corresponding to FIG. 1 are denoted by thesame reference characters.

As transparently shown in FIG. 8, each of a total of six electrodelayers 21 includes seven strip portions 210 and a joint portion 211. Theseven strip portions 210 extend in the left-right direction (conveyingdirection). The seven strip portions 210 are arranged parallel to eachother in the front-rear direction (lateral direction). The joint portion211 extends in the front-rear direction. The joint portion 211 connectsthe left ends (upstream ends in the conveying direction) of the sevenstrip portions 210 in the front-rear direction. The joint portion 211 isrestrained by a restraining member 30 in the up-down direction.Clearance F is provided between each pair of strip portions 210 adjacentto each other in the front-rear direction.

The conveying apparatus of the present embodiment and the conveyingapparatus of the first embodiment have similar functions and effectsregarding those portions having the same configuration. According to theconveying apparatus 1 of the present embodiment, the clearance F isprovided between each pair of strip portions 210 adjacent to each otherin the front-rear direction. This can reduce the area (areas of theupper and lower surfaces) of the electrode layers 21 as compared to thecase where the clearance F is not provided, and can therefore reduce acurrent value required to drive the conveying portion 2 b while ensuringa similar or higher conveying speed as compared to the case where theclearance F is not provided. According to the conveying apparatus 1 ofthe present embodiment, each pair of strip portions 210 adjacent to eachother in the front-rear direction is less likely to restrict extensionand contraction of each other's strip portion 210. The seven stripportions 210 are therefore easily extended and contracted in theleft-right direction.

<Others>

The embodiments of the conveying apparatus of the present invention aredescribed above. However, embodiments are not particularly limited tothe above embodiments. The present invention can be embodied in variousmodified or improved forms that can be implemented by those skilled inthe art.

FIG. 9 is a top view of a conveying apparatus according to a furtherembodiment (first further embodiment). Those portions corresponding toFIG. 1 are denoted by the same reference characters. As shown in FIG. 9,two conveying portions 2 b, namely right and left conveying portions 2b, may be disposed on both sides of a base portion 2 a. The leftconveying portion 2 b can be extended to the left with the base portion2 a as a starting point. The right conveying portion 2 b can be extendedto the right with the base portion 2 a as a starting point. According tothe conveying apparatus 1 of the present embodiment, an object to betransported can be transported both in the right and left directions.

FIG. 10 is a sectional view of a conveying apparatus according to afurther embodiment (second further embodiment) taken in the left-rightdirection. Those portions corresponding to FIG. 2 are denoted by thesame reference characters. As shown in FIG. 10, a backing member 31 thatalso serves as a restraining member may be provided. That is, thebacking member 31 having a restraining portion 310 at its left end maybe provided. This reduces the number of parts. Only an AC power supply40 may be provided in the power supply unit 4. This simplifies theelectrical circuit configuration. Ribs 220 extending in the front-reardirection may be provided on the conveying path 22 so as to be arrangednext to each other in the left-right direction. The right slopes(downstream-side slopes) of the ribs 220 are steeper than the leftslopes (upstream-side slopes) thereof. The object is less likely to beshifted with respect to the conveying path 22 when the conveyingapparatus 1 switches from the contracted state (see FIGS. 4A and 4C) tothe extended state (see FIGS. 4B and 4D). The object tends to be shiftedwith respect to the conveying path 22 when the conveying apparatus 1switches from the extended state to the contracted state.

The type of the restraining member 30 shown in FIGS. 1 and 2 is notparticularly limited. The restraining member 30 need only restrictdeformation and positional shifting of the base portion 2 a. Forexample, a fastening member such as a bolt and a nut or a screw, anengagement member such as a clip, a binding member such as a band ortape, or a fixing member such as an adhesive or a stapler may be used asthe restraining member 30.

The conveying apparatus 1 may not include the restraining member 30. Theconveying apparatus 1 need only be able to restrict deformation orpositional shifting of the base portion 2 a. For example, the mass(weight) of the base portion 2 a is made significantly larger than thatof the conveying portion 2 b, or the friction coefficient of the lowersurface of the base portion 2 a is made significantly larger than thatof the lower surface of the conveying portion 2 b. A tensile force maybe applied to the base portion 2 a from both sides in the front-reardirection (lateral direction). The base portion 2 a may be set bybonding the left edge of the lower protective layer 23 to the backingmember 31. The conveying apparatus 1 may not include the upper and lowerprotective layers 23 and the backing member 31.

The conveying direction on the conveying path 22 is not particularlylimited. In the case where the conveying direction is one direction, theconveying direction may be either the direction away from the baseportion 2 a or the direction toward the base portion 2 a. The conveyingdirection may be able to be switched. That is, the conveying directionmay be switched between the direction away from the base portion 2 a andthe direction toward the base portion 2 a.

The conveying path 22 may be tilted. The direction in which theconveying path 22 is tilted is not particularly limited. For example,the conveying path 22 may be tilted upward from the upstream side towardthe downstream side. Alternatively, the conveying path 22 may be tilteddownward from the upstream side toward the downstream side.

In order to control the conveying direction, the acceleration ofdeformation of the conveying path 22 varies between when the conveyingpath 22 switches from the contracted state (FIGS. 4A and 4C) to theextended state (FIGS. 4B and 4D) and when the conveying path 22 switchesfrom the extended state to the contracted state. In the case whereextension acceleration a1>contraction acceleration a2, the object W tobe transported moves mainly when the conveying path 22 switches from theextended state to the contracted state. The object W therefore tends tomove in the direction toward the base portion 2 a. In the case whereextension acceleration a1<contraction acceleration a2, the object Wmoves mainly when the conveying path 22 switches from the contractedstate to the extended state. The object W therefore tends to move in thedirection away from the base portion 2 a.

For example, the acceleration of deformation (the extension accelerationa1 and the contraction acceleration a2) can be controlled by adjustingthe frequency, waveform, maximum value Vmax, and minimum value Vmin ofthe AC voltage and the voltage value of the DC voltage Vdc shown in FIG.3, the Young's modulus of the conveying portion 2 b shown in FIG. 2, thenumber of stacked layers (the electrode layer 21, the dielectric layer20, and the electrode layer 21) in the conveying portion 2 b, and soforth. The conveying speed can be controlled similarly.

The number of stacked layers (the electrode layer 21, the dielectriclayer 20, and the electrode layer 21) in the conveying portion 2 b isnot particularly limited. Increasing the number of stacked layers canincrease the distance by which the object W is transported in one stroke(from the contracted state through the extended state to the contractedstate).

A method for disposing the electrode layer 21 on the dielectric layer 20is not particularly limited. Methods such as bonding and printing may beused. A method for disposing the restraining member 30 on the backingmember 31 is not particularly limited. The restraining member 30 may ormay not be fixed to the backing member 31.

The waveform of the voltage shown in FIG. 3 is not particularly limited.The voltage may have a triangular waveform (e.g., an isoscelestriangular waveform, a right triangular waveform, etc.), a sawtoothwaveform, a rectangular waveform, a trapezoidal waveform, etc. Thevoltage may have a continuous waveform or a pulse waveform. Theamplitude Vp of the AC voltage is desirably closer to the DC voltageVdc. It is preferable that the amplitude Vp be equal to the DC voltageVdc. This can increase the distance by which the object W is transportedin one stroke (from the contracted state through the extended state tothe contracted state).

The type of the displacement sensor 6 (detection unit) shown in FIG. 7is not particularly limited. For example, the displacement sensor 6 maybe a flexible elongation sensor or a flexible strain sensor. Theflexible elongation sensor or the flexible strain sensor may becontained in the conveying portion 2 b. The flexible elongation sensoror the flexible strain sensor may be placed independently of theconveying portion 2 b. The AC power supply 40 shown in FIG. 7 may bereplaced with a DC power supply. A predetermined waveform may beproduced from a DC voltage by the waveform adjustment unit 42. Thewaveform adjustment unit 42 may be contained in the control unit 5, theAC power supply 40, or the DC power supply.

The material of the dielectric layers 20 is not particularly limited.The dielectric layers 20 need only be made of an elastomer. For example,it is preferable to use an elastomer having high permittivity.Specifically, it is preferable to use an elastomer having a dielectricconstant (100 Hz) of 2 or more, and more preferably 5 or more, at normaltemperature. For example, an elastomer having a polar functional groupsuch as an ester group, a carboxyl group, a hydroxyl group, a halogengroup, an amide group, a sulfone group, a urethane group, or a nitrilegroup, or an elastomer containing a polar low molecular weight compoundhaving such a polar functional group is preferably used. Preferredelastomers other than H-NBR include silicone rubber,acrylonitrile-butadiene rubber (NBR), ethylene propylene diene rubber(EPDM), acrylic rubber, urethane rubber, epichlorohydrin rubber,chlorosulfonated polyethylene, chlorinated polyethylene, etc. Thematerial of the protective layers 23 is not particularly limited. Thematerial of the protective layers 23 may be similar to that of thedielectric layers 20.

The material of the electrode layers 21 is not particularly limited. Forexample, the electrode layers 21 may be made of silicone rubber, acrylicrubber, a flexible conductive material as N-NBR filled with silverpowder or carbon. The electrode layers 21 may be made of a metal or acarbon material. In order to make the electrode layers 21 stretchable,the electrode layers 21 may be formed by weaving a metal etc. into amesh pattern. The electrode layers 21 may be made of a conductivepolymer such as polyethylenedioxythiophene (PEDOT). In the case of usinga flexible conductive material containing a binder and a conductivematerial, it is preferable to use an elastomer as the binder. Preferredexamples of the elastomer include silicone rubber, NBR, EPDM, naturalrubber, styrene-butadiene rubber (SBR), acrylic rubber, urethane rubber,epichlorohydrin rubber, chlorosulfonated polyethylene, and chlorinatedpolyethylene. The conductive material is selected as appropriate fromcarbon materials such as carbon black, carbon nanotube, and graphite,metal materials such as silver, gold, copper, nickel, rhodium,palladium, chromium, titanium, platinum, iron, and alloys thereof, andconductive oxides such as indium tin oxide (ITO) and titanium oxide orzinc oxide doped with another metal such as aluminum or antimony. Asingle conductive material may be used solely, or a mixture of two ormore conductive materials may be used. The material of the wire is notparticularly limited. The material of the wire may be similar to that ofthe electrode layer 21.

The material of the restraining member 30 and the material of thebacking member 31 are not particularly limited. The restraining member30 and the backing member 31 need only be made of a resin or metalhaving higher Young's modulus than the elastomer of the dielectriclayers 20. In order to reduce the frictional resistance that is causedwhen the conveying portion 2 b slide-contacts the backing member 31, thesurface of the backing member 31 may be coated with a lubricant (arelease agent, oil, etc.). In order to reduce the contact area with theconveying portion 2 b, the surface of the backing member 31 may have aprotrusion or protrusions. The backing member 31 may be made offluororesin.

The structure, material, etc. of the cushioning member 91 shown in FIG.91 are not particularly limited. For example, the cushioning member 91may be a solid member, a porous member (honeycomb structure, cardboard,etc.), a foam member (expanded polystyrene etc.), a hollow member, etc.In the case where the cushioning material 91 is a hollow member, thecushioning member 91 may be filled with gas, liquid, etc.

The kind of the object W to be transported is not particularly limited.It is preferable that the object W bounce when the conveying portion 2 bswitches from the extended state shown in FIG. 4B to the contractedstate shown in FIG. 4C. In this regard, the object W may be powder(flour, salt, sugar, cosmetics, granules, etc.) or grains (tablets ofmedicine etc.) which have small mass.

The smaller the mass is, the larger the distance by which the object Wis transported per unit stroke is. Based on this, the objects W may besorted into a plurality of kinds by mass by the conveying apparatus 1 ofthe present embodiment.

EXAMPLES

Experiments that were conducted to examine preferred conveyingconditions for the object to be transported will be described below.

<Samples>

Table 1 shows samples used in the experiments.

TABLE 1 Size Conveying Direction [mm] × Number of Samples LateralDirection [mm] Stacked Layers Example 1 130 × 35 5 Example 2 130 × 70 5Example 3 240 × 70 5 Example 4 130 × 70 1 Example 5 130 × 70 3 Example 6130 × 70 9 Example 7 130 × 70 11

As shown in Table 1, the samples used in the experiments are Examples 1to 7. Example 2 is the conveying apparatus 1 of the first embodiment(see FIGS. 1 to 4). The materials and the thicknesses in the stackingdirection of the dielectric layer 20, the electrode layer 21, theprotective layer 23, the restraining member 30, and the backing member31 are the same in Examples 1 to 7. Each of Examples 1 to 7 has arectangular shape that is long in the conveying direction.

In Experiments 1 to 3 described below, the object W to be transported isflour. Unit particles of flour have an average particle size (diameter)of 56 μm. 2 g of flour was used. In Experiment 4 described below, theobject W to be transported is salt (specifically, aggregate of saltparticles). Salt particles have an average particle size (diameter) of400 μm. 2 g of salt was used. In Experiment 5 described below, theobject W to be transported is three tablets. Each tablet has a shortcolumnar shape. Each tablet has a diameter of 15 mm and an axial lengthof 6 mm. The mass of each tablet is 1 g. The Experiments 1 to 4 wereconducted with the object W placed near the middle of one end of theconveying portion 2 b and flattened out with a spatula.

<Experiment 1>

The sample used in Experiment 1 is Example 2 in Table 1. The forwarddirection of the conveying direction on the conveying path 22 is thedirection from left to right (the direction away from the base portion 2a) in FIGS. 1 to 4. In Experiment 1, the transport state of the object Wby Example 2 was observed with various DC voltages Vdc and various ACvoltages shown in FIG. 3. Table 2 shows the result of the experiment.

TABLE 2 Vdc [V] 0 100 200 300 400 500 600 700 800 Vpp [V] 100 Δ Δ Δ Δ ΔΔ Δ Δ Δ 200 Δ Δ Δ Δ Δ Δ Δ Δ Δ 300 Δ Δ Δ Δ Δ Δ Δ Δ ∘ 400 Δ Δ Δ Δ Δ ∘ ∘ ∘∘ 500 Δ Δ Δ ∘ ∘ ∘ ∘ ∘ ∘ 600 Δ Δ Δ ∘ ∘ ∘ ∘ ∘ ∘ 700 Δ Δ Δ Δ ∘ ∘ ∘ ∘ ∘ 800Δ Δ Δ Δ ∘ ∘ ∘ ∘ ∘

In Table 2, “◯” means that the conveying speed of the object W is high,and “Δ,” means that the conveying speed of the object W is normal. Asshown in Table 2, the object W can be transported even if only the ACvoltage is applied (even if the DC voltage Vdc is not applied).

In the case where the peak-to-peak value Vpp in FIG. 3 is large, a largeamount of Joule heat is generated from the conveying portion 2 b.Accordingly, in order to suppress generation of Joule heat, it ispreferable to reduce the peak-to-peak value Vpp (e.g., 400 V or less).However, reducing the peak-to-peak value Vpp degrades the transportstate of the object W. Accordingly, it is desirable to increase the DCvoltage Vdc (e.g., 500 V or higher) instead of reducing the peak-to-peakvalue Vpp.

Even when this experiment was conducted with a pile of object W placednear the middle of one end of the conveying portion 2 b (with the objectW not flattened out with a spatula), the object W was able to betransported as in Table 2 with the pile of the object W graduallycrumbling down.

<Experiment 2>

The samples used in Experiment 2 are Examples 1 to 3 of Table 1. Asshown in Table 1, Examples 1 to 3 are different from each other in size.The forward direction of the conveying direction of the conveying path22 is the direction from left to right (the direction away from the baseportion 2 a) in FIGS. 1 to 4. The reverse direction of the conveyingdirection of the conveying path 22 is the direction from right to left(the direction toward the base portion 2 a) in FIGS. 1 to 4.

In Experiment 2, the transport state of the object W by Examples 1 to 3was observed at various frequencies of the AC voltage shown in FIG. 3(various numbers of vibrations of the conveying portion 2 b). The DCvoltage Vdc shown in FIG. 3 was 350 V. The peak-to-peak value Vpp was700 V (i.e., the amplitude Vp=350 V). Table 3 shows the result of theexperiment.

TABLE 3 Frequency [Hz] Samples 10 20 30 40 50 60 70 80 90 100 110 120130 140 Example x x x Δ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘  Δ Δ 1 Example x x x ∘ ∘ ∘ ∘ ∘ ∘−Δ −Δ −Δ −Δ −∘ 2 Example x x ∘ ∘ ∘ ∘ Δ −Δ −Δ −Δ x x x x 3 Frequency [Hz]Samples 150 160 170 180 190 200 210 220 230 240 250 Example x −Δ −Δ x xx −Δ −Δ x x x 1 Example −∘ −∘ −∘ −∘ −∘ −∘ −Δ −Δ x x x 2 Example x x x xx x x x x x x 3

In Table 3, “◯” means that the conveying direction of the object W isthe forward direction and the conveying speed of the object W is high,“Δ” means that the conveying direction of the object W is the forwarddirection and the conveying speed of the object W is normal, “−◯” meansthat the conveying direction of the object W is the reverse directionand the conveying speed of the object W is high, “−Δ” means that theconveying direction of the object W is the reverse direction and theconveying speed of the object W is normal, and “x” means that theconveying speed of the object W is low.

As shown in Table 3, the frequency suitable for transporting the objectW is different depending on the size of Examples 1 to 3. The object Wcan be transported not only in the forward direction but also in thereverse direction by adjusting the frequency.

An audible frequency range for humans is about 20 to 20,000 Hz. In thisregard, as shown in Table 3, Examples 1 to 3 can be driven in a lowfrequency range of about 40 Hz to 100 Hz, namely in a low frequencyrange that can be hardly heard by humans. Examples 1 to 3 are thereforevery quiet (low noise).

<Experiment 3>

The samples used in Experiment 3 are Examples 2 and 4 to 7 of Table 1.As shown in Table 1, Examples 2 and 4 to 7 are different from each otherin the number of stacked layers. The number of stacked layers refers tothe number of dielectric layers 20 in the case where the electrodelayers 21 and the dielectric layers 20 are alternately stacked. Forexample, if the number of stacked layers is 9, this means that thenumber of dielectric layers 20 is 9 and the number of electrode layers21 is 10.

In Experiment 3, as in Experiment 2, the transport state of the object Wby Examples 2 and 4 to 7 was observed at various frequencies of the ACvoltage shown in FIG. 3 (various numbers of vibrations of the conveyingportion 2 b). The DC voltage Vdc shown in FIG. 3 was 350 V. Thepeak-to-peak value Vpp was 700 V (i.e., the amplitude Vp=350 V). Table 4shows the result of the experiment. Definitions of the forwarddirection, the reverse direction, “◯,” “Δ,” “−◯,” “−Δ,” and “x” and aresimilar to Experiment 2.

TABLE 4 Frequency [Hz] Samples 10 20 30 40 50 60 70 80 90 100 110 120130 140 Example x x x Δ Δ Δ x x x x x x x x 4 Example x x x Δ Δ Δ x x xx x x x x 5 Example x x x ∘ ∘ ∘ ∘ ∘ ∘ −Δ −Δ −Δ −Δ −∘ 2 Example x x x ∘ ∘∘ ∘ ∘ ∘ ∘ ∘ x x x 6 Example x x x ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘  ∘ 7 Frequency[Hz] Samples 150 160 170 180 190 200 210 220 230 240 250 Example x x x xx x x x x x x 4 Example x x x x x x x x x x x 5 Example −∘ −∘ −∘ −∘ −∘−∘ −Δ −Δ x x x 2 Example x x x x x x x x x x x 6 Example  ∘  ∘ Δ Δ x x xx x x x 7

As shown in Table 4, the frequency suitable for transporting the objectW is different depending on the number of stacked layers of Examples 2and 4 to 7. The object W can be transported not only in the forwarddirection but also in the reverse direction by adjusting the frequency.

An audible frequency range for humans is about 20 to 20,000 Hz. In thisregard, as shown in Table 4, Examples 2 and 4 to 7 can be driven in alow frequency range of about 40 Hz to 100 Hz, namely in a low frequencyrange that can be hardly heard by humans. Examples 2 and 4 to 7 aretherefore very quiet (low noise).

<Experiment 4>

The sample used in Experiment 4 is Example 2 of Table 1. Experiment 4 isdifferent from Experiment 1 only in the kind of the object W. InExperiment 4, salt rather than flour (Experiment 1) was used as theobject W. Table 5 shows the result of the experiment.

TABLE 5 Vdc[V] 100 200 300 400 500 600 700 800 Vpp [V] 100 Δ Δ Δ Δ Δ Δ ΔΔ 200 Δ Δ Δ Δ Δ Δ Δ Δ 300 Δ Δ Δ Δ Δ Δ ∘ ∘ 400 Δ Δ Δ ∘ ∘ ∘ ∘ ∘ 500 Δ Δ ∘∘ ∘ ∘ ∘ ∘ 600 Δ Δ ∘ ∘ ∘ ∘ ∘ ∘ 700 Δ Δ Δ ∘ ∘ ∘ ∘ ∘ 800 Δ Δ Δ ∘ ∘ ∘ ∘ ∘

In Table 5, “◯” means that the conveying speed of the object W is high,and “Δ” means that the conveying speed of the object W is normal. Asshown in Table 5, the object W can be transported even if the object Wis salt.

Even when this experiment was conducted with a pile of object W placednear the middle of one end of the conveying portion 2 b (with the objectW not flattened out with a spatula), the object W was able to betransported as in Table 5 with the pile of the object W graduallycrumbling down.

<Experiment 5>

The sample used in Experiment 5 is Example 2 of Table 1. Experiment 5 isdifferent from Experiment 1 only in the kind of the object W. InExperiment 5, tablets rather than flour (Experiment 1) were used as theobject W. Table 6 shows the result of the experiment.

TABLE 6 Vdc [V] 100 200 300 400 500 600 700 800 Vpp [V] 100 Δ Δ Δ Δ Δ ΔΔ Δ 200 Δ Δ Δ Δ Δ Δ Δ Δ 300 Δ Δ Δ Δ ∘ ∘ ∘ ∘ 400 Δ Δ ∘ ∘ ∘ ∘ ∘ ∘ 500 Δ Δ∘ ∘ ∘ ∘ ∘ ∘ 600 Δ Δ ∘ ∘ ∘ ∘ ∘ ∘ 700 Δ Δ Δ ∘ ∘ ∘ ∘ ∘ 800 Δ Δ Δ ∘ ∘ ∘ ∘ ∘

In Table 6, “◯” means that the conveying speed of the object W is high,and “Δ” means that the conveying speed of the object W is normal. Asshown in Table 6, the object W can be transported even if the object Wis tablets.

<Regarding Experiments 6 to 9>

The ordinate and the abscissa in FIGS. 11 to 24 regarding Experiments 6to 9 are represented by arbitrary units. The graphs of the same kind canbe compared to each other. That is, FIGS. 11, 13, 15 to 18, 20, and 22in which the abscissa represents time and the ordinate representsvoltage and position can be compared to each other. FIGS. 12, 14, 19,21, and 24 in which the abscissa represents time and the ordinaterepresents distance can be compared to each other.

The “position” on the ordinate of FIGS. 11, 13, 15 to 18, 20, and 22 isthe position in the conveying direction (left-right direction) of thedetection position P4 that is set on the conveying path 22 as shown inFIG. 7. The base point (point 0) of the position is an upstream end(left end) P5 of the conveying path 22.

The “distance” on the ordinate of FIGS. 12, 14, 19, 21, and 24 is thedistance E in the conveying direction between a position P6 of theobject W and the detection position P4 as shown in FIG. 7. The distanceE before transport is defined as “0.” The experiments were shot with ahigh speed camera. The detection position P4, the position P6 of theobject W, and the distance E were measured from the images of the highspeed camera.

As shown in FIG. 7, the position P6 is set on the upstream side in theconveying direction of the detection position P4. Accordingly, in thecase where the distance E changes in the positive direction from 0 asthe object W is transported, this means that the object W has moved tothe upstream side (in the reverse direction of the conveying direction).On the other hand, in the case where the distance E changes in thenegative direction from 0 as the object W is transported, this meansthat the object W has moved to the downstream side (in the forwarddirection of the conveying direction). The object W is zirconia beads(specifically, aggregate of zirconia beads). The zirconia beads have anaverage particle size (diameter) of 300 μm.

<Experiment 6>

In Experiment 6, the difference in conveying speed depending on the typeof waveform (rectangular waveform, triangular waveform) of the voltage(DC voltage whose polarity is not inverted) was examined. The sampleused in Experiment 6 is Example 2 of Table 1. FIG. 11 shows a change inposition with time in the case where the voltage has a rectangularwaveform. FIG. 12 shows a change in distance with time in the case ofFIG. 11. FIG. 13 shows a change in position with time in the case wherethe voltage has a right triangular waveform with a sharply increasinggradient to the right. FIG. 14 shows a change in distance with time inthe case of FIG. 13. The voltage waveforms shown in FIGS. 11 and 13 wereproduced by the waveform adjustment unit 42 shown in FIG. 7.

In the Case where the Voltage has a Rectangular Waveform

First, an example in which the voltage has a rectangular waveform willbe described. As shown in FIG. 11, a waveform G of a change in voltageM1 with time (a waveform for one period; the same applies to thefollowing description) includes a boost section H and a step-downsection K. In the boost section H, the voltage M1 switches from off toon. That is, the voltage M1 increases with time. The conveying portion 2b is extended in the conveying direction according to the boost sectionH. The detection position P4 is therefore displaced to the downstreamside. A time differential value (gradient) of the voltage M1 in theboost section H corresponds to the extension acceleration of theconveying portion 2 b. The larger the absolute value of the timedifferential value is, the larger the extension acceleration of theconveying portion 2 b is. In the step-down section K, the voltage M1switches from on to off. That is, the voltage M1 decreases with time.The conveying portion 2 b is contracted in the conveying directionaccording to the step-down section K. The detection position P4 istherefore displaced to the upstream side. A time differential value(gradient) of the voltage M1 in the step-down section K corresponds tothe contraction acceleration of the conveying portion 2 b. The largerthe absolute value of the time differential value is, the larger thecontraction acceleration of the conveying portion 2 b is. In the casewhere the waveform G is a rectangular waveform, the absolute value ofthe time differential value of the voltage M1 in the boost section H isthe same as that of the time differential value of the voltage M1 in thestep-down section K.

As shown in FIG. 12, in the case where the waveform G is a rectangularwaveform, the distance E (specifically, the distance E in the conveyingdirection between the position P6 of the object W and the detectionposition P4) shown in FIG. 7 changes in the negative direction from 0.That is, in the case where the waveform G is a rectangular waveform, theobject W can be transported to the downstream side.

However, in the case where the waveform G is a rectangular waveform,there are a plurality of sections where the distance E changes in thepositive direction, as shown by hatched areas in FIG. 12. That is, thereare a plurality of sections where the object W moves to the upstreamside (reverse movement sections).

In the Case where the Voltage has a Triangular Waveform

An example in which the voltage has a right triangular waveform with asharply increasing gradient to the right (a later point in time) will bedescribed. As shown in FIG. 13, a waveform G, for one period, of achange in voltage M2 with time includes a boost section H and astep-down section K. The absolute value of a time differential value ofthe voltage M2 in the boost section H is smaller than that of the timedifferential value of the voltage M2 in the step-down section K.

As shown in FIG. 14, the distance E shown in FIG. 7 (specifically, thedistance E in the conveying direction between the position P6 of theobject W and the detection position P4) changes in the negativedirection from 0. That is, in the case where the waveform G is a righttriangular waveform with a sharply increasing gradient to the right, theobject W can be transported to the downstream side.

The absolute value of the time differential value of the voltage M2 inthe boost section H is smaller than that of the time differential valueof the voltage M2 in the step-down section K. Accordingly, the conveyingportion 2 b is slowly extended and quickly contracted. The object W istherefore less likely to be shifted with respect to the conveying path22 when the conveying portion 2 b is extended. The object W thus tendsto move to the downstream side according to extension of the conveyingpath 22. Moreover, the object W tends to be shifted with respect to theconveying path 22 when the conveying path 22 is contracted. The object Wis therefore less likely to move according to contraction of theconveying path 22.

As described above, in the case where the absolute value of the timedifferential value of the voltage M2 in the boost section H is smallerthan that of the time differential value of the voltage M2 in thestep-down section K, the object W is less likely to move in the reversedirection as shown in FIG. 14. As shown in FIGS. 12 and 14, theconveying speed can be increased at the voltage M2 with respect to thevoltage M1.

<Experiment 7>

In Experiment 7, the difference in conveying speed depending on the typeof waveform (four types of triangular waveforms) of the voltage (DCvoltage whose polarity is not inverted) was examined. The sample used inExperiment 7 is Example 2 of Table 1. FIG. 15 shows a change in positionwith time in the case where the voltage has a right triangular waveformwith a sharply increasing gradient to the left. FIG. 16 shows a changein position with time in the case where the voltage has an isoscelestriangular waveform. FIG. 17 shows a change in position with time in thecase where the voltage has a triangular waveform with a sharplyincreasing gradient to the right. FIG. 18 shows a change in positionwith time in the case where the voltage has a right triangular waveformwith a sharply increasing gradient to the right. FIG. 19 shows a changein distance with time in the case of FIGS. 15 to 18. The waveforms ofvoltages M3 to M6 shown in FIGS. 15 to 18 were produced by the waveformadjustment unit 42 shown in FIG. 7. The waveform of the voltage M6 inFIG. 18 is similar to that of the voltage M2 in FIG. 13.

As shown in FIGS. 15 to 18, a waveform G, for one period, of a change involtage M3 to M6 with time includes a boost section H and a step-downsection K. As shown in FIG. 15, in the case where the voltage M3 has aright triangular waveform with a sharply increasing gradient to the left(an earlier point in time), the absolute value of a time differentialvalue of the voltage M3 in the boost section H is larger than that ofthe time differential value of the voltage M3 in the step-down sectionK. As shown in FIG. 16, in the case where the voltage M4 has anisosceles triangular waveform, the absolute value of a time differentialvalue of the voltage M4 in the boost section H is the same as that ofthe time differential value of the voltage M4 in the step-down sectionK. As shown in FIG. 17, in the case where the voltage M5 has atriangular waveform with a sharply increasing gradient to the right (alater point in time), the absolute value of a time differential value ofthe voltage M5 in the boost section H is slightly smaller than that ofthe time differential value of the voltage M5 in the step-down sectionK. As shown in FIG. 18, in the case where the voltage M6 has a righttriangular waveform with a sharply increasing gradient to the right, theabsolute value of a time differential value of the voltage M6 in theboost section H is smaller than that of the time differential value ofthe voltage M6 in the step-down section K.

As shown in FIG. 19, in the case where the waveform G is any of the fourtypes of triangular waveforms, the object W can be transported althoughthere is differences in conveying direction and conveying speed amongthe four triangular waveforms. As shown by M5 and M6 in FIG. 19, theobject W is less likely to move in the reverse direction if the absolutevalue of the time differential value of the voltage M5, M6 in the boostsection H is made smaller than that of the time differential value ofthe voltage M5, M6 in the step-down section K. Moreover, the smaller theratio between the absolute values (=(the absolute value of the timedifferential value of the voltage M5, M6 in the boost section H)/(theabsolute value of the time differential value of the voltage M5, M6 inthe step-down section K) is, the higher the conveying speed is. As shownby M3 in FIG. 19, the object W can be moved in the reverse direction bymaking the absolute value of the time differential value of the voltageM3 in the boost section H larger than that of the time differentialvalue of the voltage M3 in the step-down section K.

<Experiment 8>

In Experiment 8, the voltage (DC voltage whose polarity is not inverted)had a right triangular waveform with a sharply increasing gradient tothe right (a later point in time). Moreover, in Experiment 8, theinterval during which the voltage is off is set between each pair ofwaves that are located next to each other in chronological order. Theconveying speed was examined in Experiment 8. The sample used inExperiment 8 is Example 2 of Table 1. FIG. 20 shows a change in positionwith time in the case where the voltage has a right triangular waveformwith a sharply increasing gradient to the right and the interval duringwhich the voltage is off is set between each pair of waves that arelocated next to each other in chronological order. FIG. 21 shows achange in distance with time in the case of FIG. 20. In FIG. 21, thevoltage M2 of FIG. 14 is shown together with the voltage M7 of FIG. 20for comparison.

As shown in FIGS. 13 and 20, the waveform G of the voltage M2 is thesame as that of the voltage M7. The period, wavelength, and peak-to-peakvalue of the waveform G of the voltage M2 are the same as those of thewaveform G of the voltage M7. However, as shown by hatched areas in FIG.20, the interval during which the voltage is off is set between eachpair of waves G of the voltage M7 which are located next to each other.The width of the interval is the same as that of the waveform G. Asshown in FIG. 13, the interval during which the voltage is off is notset between each pair of waves G of the voltage M2 which are locatednext to each other. The waves G are continuous. The frequency of thevoltage M7 is therefore half the frequency of the voltage M2.

As shown in FIG. 21, the conveying speed is substantially the samebetween the voltage M2 (with no interval) and the voltage M7 (with theintervals). At the voltage V7, the frequency can be reduced with respectto the voltage M2 while ensuring a similar transport speed.

<Experiment 9>

In Experiment 9, the voltage (DC voltage whose polarity is not inverted)had a right triangular waveform with a sharply increasing gradient tothe right (a later point in time), and the conveying speed was examined.The sample used in Experiment 9 is Example 2 of Table 1 with the sevenstrip portions 210, the joint portion 211, and the clearance F of FIG. 8formed in all of the electrode layers 21. FIG. 22 shows a change inposition with time in the case where the voltage has a right triangularwaveform with a sharply increasing gradient to the right. FIG. 23 showsacceleration of extension/contraction of the conveying portion in thecase of FIG. 22. FIG. 24 shows a change in distance with time in thecase of FIG. 22. In FIGS. 23 and 24, a part of the voltage M2 in FIG. 14(a part corresponding to time 0 to 200) is shown together with thevoltage M8 of FIG. 22 for comparison. In FIG. 23, the positive directionof the ordinate represents acceleration in the extension direction, andthe negative direction of the ordinate represents acceleration in thecontraction direction.

As shown in FIGS. 13 and 22, the waveform G of the voltage M2 is thesame as that of the voltage M8. The period, wavelength, and peak-to-peakvalue of the waveform G of the voltage M2 are the same as those of thewaveform G of the voltage M8. As shown in FIG. 23, the extensionacceleration and the contraction acceleration of the conveying portion 2b are larger at the voltage M8 (the sample of Experiment 9, shown bysolid line) than at the voltage M2 (Example 2, shown by dashed line).Particularly at the voltage M8, the contraction acceleration can beincreased with respect to the extension acceleration. Namely, theconveying portion 2 b can be slowly extended and quickly contracted.Accordingly, as shown in FIG. 24, the conveying speed can be higher atthe voltage M8 (the sample of Experiment 9) than at the voltage M2(Experiment 2).

As shown in FIG. 1 (Example 2 of Table 1) and FIG. 8 (the sample ofExperiment 9), the electrode layers 21 of the sample of Experiment 9have a smaller area as compared to Example 2 as viewed from above. Thiscan reduce a current value required to drive the conveying portion 2 b.

DESCRIPTION OF THE REFERENCE NUMERALS

-   -   1: conveying apparatus    -   2: conveying member    -   2 a: base portion    -   2 b: conveying portion    -   20: dielectric layer    -   21: electrode layer    -   210: strip portion    -   211: joint portion    -   22: conveying path    -   220: rib    -   23: protective layer    -   30: restraining member    -   31: backing member    -   310: restraining portion    -   32: connector    -   4: power supply unit    -   40: AC power supply    -   41: DC power supply    -   42: waveform adjustment unit    -   5: control unit    -   6: displacement sensor (detection unit)    -   91: cushioning member    -   10: conveying unit    -   E: distance    -   F: clearance    -   G: waveform    -   H: boost section    -   K: step-down section    -   L1: clearance in up-down direction    -   O1: overlapping portion    -   Vdc: DC voltage    -   Vmax: maximum value    -   Vmin: minimum value    -   Vp: amplitude    -   Vpp: peak-to-peak value    -   W: object to be transported    -   a1: extension acceleration    -   a2: contraction acceleration

1. A conveying apparatus, comprising: a conveying member that has adielectric layer having insulating properties and made of an elastomerand a pair of electrode layers placed on both front and back sides ofthe dielectric layer and having conductive properties, and that isdivided into a base portion and a conveying portion being more easilyelastically deformed than the base portion and having on its surface aconveying path on which an object to be transported is transported; anda power supply unit that applies between the pair of electrode layers avoltage that changes periodically with time, wherein the conveyingportion is elastically extended and contracted with the base portion asa starting point according to a change in the voltage, so that theobject is transported on the conveying path.
 2. The conveying apparatusaccording to claim 1, wherein a conveying direction is a direction inwhich the conveying path extends on the surface of the conveyingportion, and the base portion is placed at one end or the other end ofthe conveying path in the conveying direction.
 3. The conveyingapparatus according to claim 1, further comprising: a restraining memberthat restrains a part of the conveying member, and the base portion isformed by restraining the part of the conveying member by therestraining member.
 4. The conveying apparatus according to claim 1,wherein the conveying direction is the direction in which the conveyingpath extends on the surface of the conveying portion, and a lateraldirection is a direction perpendicular to the conveying direction, and atotal length of the conveying path in the conveying direction is largerthan that of the conveying path in the lateral direction.
 5. Theconveying apparatus according to claim 1, wherein the conveying memberhas a protective layer having insulating properties and made of anelastomer, the protective layer being placed on the frontmost electrodelayer.
 6. The conveying apparatus according to claim 1, furthercomprising: a backing member that is placed on a back side of theconveying member and that slide-contacts the conveying portion when theconveying portion is elastically extended and contracted.
 7. Theconveying apparatus according to claim 1, wherein the power supply unithas a DC power supply capable of supplying a voltage whose polarity isnot inverted or an AC power supply capable of supplying a voltage whosepolarity is inverted and a waveform adjustment unit that adjusts awaveform of the voltage that is supplied from the DC power supply or theAC power supply.
 8. The conveying apparatus according to claim 1,wherein the power supply unit has a DC power supply capable of supplyinga bias voltage whose polarity is not inverted and which has constantmagnitude and an AC power supply capable of supplying a voltage whosepolarity is inverted.
 9. The conveying apparatus according to claim 1,wherein the voltage that is applied between the pair of electrode layersby the power supply unit is a DC voltage whose polarity is not inverted.10. The conveying apparatus according to claim 9, wherein a waveform,for one period, of a change in the DC voltage with time has a boostsection where the DC voltage increases with time and a step-down sectionwhere the DC voltage decreases with time, and an absolute value of atime differential value of the DC voltage in the boost section issmaller than that of the time differential value of the DC voltage inthe step-down section.
 11. The conveying apparatus according to claim 1,further comprising: a control unit that controls the power supply unit.12. The conveying apparatus according to claim 11, further comprising: adetection unit that detects extension and contraction of the conveyingportion, and the control unit controls the power supply unit based on adetection value of the detection unit.
 13. The conveying apparatusaccording to claim 1, wherein the conveying direction is the directionin which the conveying path extends on the surface of the conveyingportion, and the lateral direction is the direction perpendicular to theconveying direction, the electrode layer has a plurality of stripportions extending in the conveying direction and arranged next to eachother in the lateral direction, and clearance is provided between a pairof the strip portions adjacent to each other in the lateral direction.